There are a few reasons: If your liquid foundation tends to get cakey by afternoon, a spritz of water lets you smooth it without adding more, says makeup artist Matthew Nigara. Or, if you're a mineral makeup convert, you'll see that a post-application mist turns its matte finish more luminous. You can also use a mist before applying moisturizer, which is absorbed more readily into damp skin. Of course, you can get the same effect by filling a spray bottle with (free) tap water. But if you're the type who springs for two-ply toilet paper and fancy, prewashed lettuce, you might enjoy the luxury of a sleek, travel-ready can (like Evian Brumisateur, $10).